Efficient calf thymus DNA condensation upon binding with novel bile acid polyamine amides

Practical Synthesis of Antimicrobial Long Linear Polyamine Succinamides

There are many severe bacterial infections notorious for their ability to become resistant to clinically relevant antibiotics. Indeed, antibiotic resistance is a growing threat to human health, further exacerbated by the lack of new antibiotics. We now describe the practical synthesis of a series of substituted long linear polyamines that produce rapid antibacterial activity against both Gram-positive and Gram-negative bacteria, including meticillin-resistant Staphylococcus aureus. These compounds also reduce biofilm formation in Pseudomonas aeruginosa. The most potent analogues are thermine, spermine, and 1,12-diaminododecane homo- and heterodimeric polyamine succinic acid amides. They are of the order of activity of the aminoglycoside antibiotics kanamycin and tobramycin as positive controls. Their low human cell toxicity is demonstrated in ex vivo hemolytic assays where they did not produce even 5% hemolysis of human erythrocytes. These long, linear polyamines are a new class of broad-spectrum antibacterials active against drug-resistant pathogens.

Design and synthesis of hybrid compounds as novel drugs and medicines

The development of highly effective conjugate chemistry approaches is a way to improve the quality of drugs and of medicines. The aim of this paper is to highlight and review such hybrid compounds and the strategies underpinning their design. A variety of unique hybrid compounds provide an excellent toolkit for novel biological activity, e.g. anticancer and non-viral gene therapy (NVGT), and as templates for killing bacteria and preventing antibiotic drug resistance. First we discuss the anticancer potential of hybrid compounds, containing daunorubicin, benzyl- or tetrahydroisoquinoline-coumarin, and cytotoxic NSAID-pyrrolizidine/indolizine hybrids, then NVGT cationic lipid-based delivery agents, where steroids or long chain fatty acids as the lipid moiety are bound to polyamines as the cationic moiety. These polyamines can be linear as in spermidine or spermine, or on a polycyclic sugar template, aminoglycosides kanamycin and neomycin B, the latter substituted with six amino groups. They are highly efficient for the delivery of both fluorescent DNA and siRNA. Molecular precedents can be found for the design of hybrid compounds in the natural world, e.g., squalamine, the first representative of a previously unknown class of natural antibiotics of animal origin. These polyamine-bile acid (e.g. cholic acid type) conjugates display many exciting biological activities with the bile acids acting as a lipidic region and spermidine as the polycationic region. Analogues of squalamine can act as vectors in NVGT. Their natural role is as antibiotics. Novel antibacterial materials are urgently needed as recalcitrant bacterial infection is a worldwide problem for human health. Ribosome inhibitors founded upon dimers of tobramycin or neomycin, bound as ethers by a 1,6-hexyl linker or a more complex diether-disulfide linker, improved upon the antibiotic activity of aminoglycoside monomers by 20- to 1200-fold. Other hybrids, linked by click chemistry, conjugated ciprofloxacin to neomycin, trimethoprim, or tedizolid, which is now in clinical trials.

A Cu²⁺-selective fluorescent chemosensor based on BODIPY with two pyridine ligands and logic gate

A novel near-infrared fluorescent chemosensor based on BODIPY (Py-1) has been synthesized and characterized. Py-1 displays high selectivity and sensitivity for sensing Cu(2+) over other metal ions in acetonitrile. Upon addition of Cu(2+) ions, the maximum absorption band of Py-1 in CH3CN displays a red shift from 603 to 608 nm, which results in a visual color change from pink to blue. When Py-1 is excited at 600 nm in the presence of Cu(2+), the fluorescent emission intensity of Py-1 at 617 nm is quenched over 86%. Notably, the complex of Py-1-Cu(2+) can be restored with the introduction of EDTA or S(2-). Consequently, an IMPLICATION logic gate at molecular level operating in fluorescence mode with Cu(2+) and S(2-) as chemical inputs can be constructed. Finally, based on the reversible and reproducible system, a nanoscale sequential memory unit displaying "Writing-Reading-Erasing-Reading" functions can be integrated.

Asymmetrical N4,N9-diacyl spermines: SAR studies of nonviral lipopolyamine vectors for efficient siRNA delivery with silencing of EGFP reporter gene

Our aim is to study the effects of varying the two acyl moieties in synthesized N(4),N(9)-diacyl spermines on siRNA formulations and their delivery efficiency in cell lines. Six novel asymmetrical lipopolyamines, [N(4)-cholesteryloxy-3-carbonyl-N(9)-oleoyl-, N(4)-decanoyl-N(9)-oleoyl-, N(4)-decanoyl-N(9)-stearoyl-, N(4)-lithocholoyl-N(9)-oleoyl-, N(4)-myristoleoyl-N(9)-myristoyl-, and N(4)-oleoyl-N(9)-stearoyl]-1,12-diamino-4,9-diazadodecane, were assessed for their abilities to bind to siRNA, studied using a RiboGreen intercalation assay, and to form nanoparticles. Their siRNA delivery efficiencies were quantified in FEK4 primary skin cells and in an immortalized cancer cell line (HtTA) using a fluorescein-tagged siRNA, and compared with formulations of N(4),N(9)-dioleoyl-1,12-diamino-4,9-diazadodecane and of a leading transfecting agent, TransIT-TKO. Transfection was measured in terms of siRNA delivery and silencing of EGFP reporter gene in HeLa cells. By incorporating two different acyl moieties, changing their length and oxidation level in a controlled manner, we show efficient fluorescein-tagged siRNA formulation, delivery, and knock-down of EGFP reporter gene. N(4)-Oleoyl-N(9)-stearoyl spermine and N(4)-myristoleoyl-N(9)-myristoyl spermine are effective siRNA delivery vectors typically resulting in 89% cell delivery and gene silencing to 34% in the presence of serum, comparable with the results obtained with TransIT-TKO; adding a second lipid chain is better than incorporating a steroid moiety.

Synthesis and antimicrobial evaluation of bile acid tridentate conjugates

Two series of novel bile acid tridentate conjugates with different linkers were synthesized and characterized, and their biological activities in vitro were evaluated. The procedure was straightforward and efficient to be carried out with high overall yield. The antimicrobial activity of the synthesized compounds against Saccharomyces cerevisiae, Aspergillus niger, Escherichia coli and Staphylococcus aureus was investigated in vitro. The best activity of minimal inhibitory concentrations (MICs) for 1c, 1c', 2c and 2c' against S. cerevisiae was up to 0.125 microg/mL.

Study by optical spectroscopy and molecular dynamics of the interaction of acridine-spermine conjugate with DNA

We report a spectroscopic and theoretical study of the interaction between double-stranded oligonucleotides containing either adenine-thymine or guanine-cytosine alternating sequences and N1-(Acridin-9-ylcarbonyl)-1,5,9,14,18-pentazaoctadecane, or ASC, which is formed by the covalent bonding of spermine and 9-amidoacridine moieties via a trimethylene chain. Solutions containing the oligonucleotides and the conjugate at different molar ratios were studied using complementary spectroscopic techniques, including electronic absorption, fluorescence emission, circular dichroism, and Raman spectroscopy. The spectroscopical properties of ASC at both the vibrational and the electronic levels were described by means of ab initio quantum-chemical calculations on 9-amidoacridine, used as a model compound. Molecular dynamics calculations, based on the QM/MM methodology, were also performed using previously docked structures of two oligonucleotide-ASC complexes containing the A-T and the G-C sequence. Our data, taken all together, allowed us to demonstrate that conjugation of spermine to acridine modulates and gives additional properties to the interaction of the latter with DNA. As the ASC molecule has a high affinity by the polyamine transport system, these results are promising for their application in the development of new anti-tumour drugs.

Synthesis and antimicrobial activity of 7-fluoro-3-aminosteroids

A series of 7-fluoro-3-aminosteroids were synthesized and their in vitro antimicrobial activities were evaluated against Gram-positive and Gram-negative bacteria. The nucleophilic fluorination of several 7beta-hydroxysteroids by diethylaminosulfur trifluoride in n-pentane, followed by reductive amination of the resulting 7-fluoro-3-ketosteroids with spermidine in the presence of NaBH(3)CN, afforded 7-fluoro-3-aminosteroids in high yield. Compound 25 showed the highest antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pyogenes, and Escherichia coli.

Chemical and metabolic transformations of selected bile acids

This article surveys chemical transformations of selected bile acids. Chemical transformations were initially carried out with the aim of determining the structure of bile acids. More recently they have been concerned with bile acid interconversions as well as with the synthesis of steroid hormones, vitamins and therapeutc agents. Studies of similarities and differences in the biosynthesis of bile acids from cholesterol have occupied many researches. However, this article reviews only papers dealing with the synthesis of potential intermediates in the biosynthesis of bile acids. Steroid hormones such as pregnenolone, progesterone and testosterone are synthesized from methyl thiodeoxycholate whereas cortisone is synthesized from methyl deoxycholiate. Numerous papers and patents devoted to the synthesis of ursodeoxycholic acid from cholic or chenodeoxycholic acid testify to its effectiveness in the treatment of cholelithiasis. Chenodeoxycholic acid appears to be an excellent precursor in the synthesis of steroid plant growth regulators, as well as in the synthesis of metabolites and vitamin D analogues. Chirality of bile acids has been exploited in the synthesis of cyclic and acyclic receptors and solvents. Cholic and deoxycholic acids have been used to create new macrocyclic structures which show different capacities to bind and transport other compounds. Another important trend in the chemistry of bile acids is their application in combinatorial chemistry.

Varying the unsaturation in N4,N9-dioctadecanoyl spermines: nonviral lipopolyamine vectors for more efficient plasmid DNA formulation

PURPOSE

The aim of the study is to analyze the effect of varying the degree of unsaturation in synthesized N4,N9-dioctadecanoyl spermines on DNA condensation and then to compare their transfection efficiency in cell culture.

METHODS

The N4,N9-di-C18 lipopolyamines-saturated (stearoyl), C9-cis- (oleoyl), and C9,12-di-cis- (linoleoyl)-were synthesized from the naturally occurring polyamine spermine. The ability of these novel compounds to condense DNA and form nanoparticles was studied using ethidium bromide fluorescence quenching and nanoparticle characterization techniques. Transfection efficiency was studied in several primary skin cells (FEK4, FCP4, FCP5, FCP7, and FCP8) and in an immortalized cancer cell line (HtTA) and was compared with the commercially available nonliposomal transfection formulation Transfectam (dioctadecylamidoglycyl spermine), which also contains two saturated C18 lipid chains.

RESULTS

N4,N9-Dilinoleoyl spermine (C18, di-cis-9,12) is efficient at circular plasmid DNA (pEGFP) condensation and gives the most effective transfection in a series of primary skin cells and cancer cell lines at low charge ratios of 5.5 (+/-ammonium/phosphate).

CONCLUSIONS

The dienoic fatty acyl spermine conjugate N4,N9-dilinoleoyl spermine efficiently condenses DNA and achieves the highest transfection levels among the studied lipopolyamines in cultured cells.

DNA-binding by functionalized gold nanoparticles: mechanism and structural requirements

A family of nanoparticles featuring surfaces of varying hydrophobicity was synthesized. The efficiency of DNA-binding was determined, demonstrating in a fivefold modulation in binding a 37-mer DNA strand. Nanoparticle-binding causes a reversible conformational change in the DNA structure, as demonstrated by circular dichroism and fluorescence experiments. Furthermore, the affinity of the nanoparticle for the DNA can be regulated by external agents, though stability of the complex is observed at relatively high ionic strengths.

Deoxycholic acid-conjugated chitosan oligosaccharide nanoparticles for efficient gene carrier

To develop chitosan based efficient gene carriers, highly purified chitosan oligosaccharides (COSs) were chemically modified with deoxycholic acid (DOCA). Owing to the amphiphilic characters, the DOCA-conjugated COSs (COSDs) formed self-aggregated nanoparticles in aqueous milieu. The physicochemical characterization revealed that the particle size of the nanoparticles was in the range of 200 approximately 240 nm and the critical aggregation concentration (cacs) was 0.012 approximately 0.046 g/L, depending on the degree of substitution (DS). As efficient gene carriers, the COSD nanoparticles showed superior gene condensation and protection of condensed gene from endonuclease attack than unmodified COSs. Furthermore, COSDs showed great potential for gene carrier with the high level of gene transfection efficiencies, even in the presence of serum. Considered with the negligible cytotoxic effects, DOCA-modified chitosan oligosaccharides can be considered as potential candidates for efficient non-viral gene carriers.

Design, synthesis, and biological evaluation of indenoisoquinoline topoisomerase I inhibitors featuring polyamine side chains on the lactam nitrogen

The indenoisoquinolines are a class of noncamptothecin topoisomerase I inhibitors that display significant cytotoxicity in human cancer cell cultures. They offer a number of potential advantages over the camptothecins, including greater chemical stability, formation of more persistent cleavage complexes, and induction of a unique pattern of DNA cleavage sites. Molecular modeling has suggested that substituents on the indenoisoquinoline lactam nitrogen would protrude out of the DNA duplex in the ternary cleavage complex through the major groove. This indicates that relatively large substituents in that location would be tolerated without compromising biological activity. As a strategy for increasing the potencies and potential therapeutic usefulness of the indenoisoquinolines, a series of compounds was synthesized containing polyamine side chains on the lactam nitrogen. The rationale for the synthesis of these compounds was that the positively charged ammonium cations would increase DNA affinity through electrostatic binding to the negatively charged DNA backbone, and the polyamines might also facilitate cellular uptake by utilization of polyamine transporters. The key step in the synthesis involved the condensation of Schiff bases, containing protected amine side chains, with substituted homophthalic anhydrides, to afford cis-3-aryl-4-carboxy-1-isoquinolones. These isoquinolones were then converted to indenoisoquinolines with thionyl chloride. Although monoamines were much more potent than the lead compound, no significant increase in potency was observed through incorporation of additional amino groups in the side chain. However, one of the monoamine analogues, which features a bis(2-hydroxyethyl)amino group in the side chain, proved to be one of the most cytotoxic indenoisoquinoline synthesized to date, with a GI50 mean-graph midpoint (MGM) of 0.07 microM in the NIH human cancer cell culture screen, and topoisomerase I inhibitory activity comparable to that of camptothecin.